Could Hong Kong policemen face prosecution for violent acts committed during crowd control?
Police officers involved in riot control operations during Occupy Central could face legal action if the use of pepper spray was to punish protesters, says academic

I was shown this disturbing video footage yesterday (below), which has apparently been circulating on social media for quite some time.
The clip features a man, approximately in his sixties, standing between protesters with their umbrellas and police in their anti-riot gear, separated by metal fencing. Bidding to ease the tension (after an unsuccessful attempt by the crowd to charge the police), the man shouts to the crowd at the top of his voice: “Do not charge, do not get irritated, it is of no use!” All of a sudden, a police inspector (in a white shirt) taps the man on the shoulder who then instinctively turns around. Without mercy, the officer applies pepper spray right into the man’s face. My gut reaction was: “This has got to be criminal!”
In fact, the legal consequences for the officer could be grave. The use of pepper spray is regulated under Hong Kong law by the Firearms and Ammunitions Ordinance, Cap 238 (FAO), which provides that anyone who uses any weapon for the discharge of noxious liquid (including aerosol containing such liquid) in a manner likely to injure another is potentially criminally liable to imprisonment for up to seven years (sections 2(e) and 22 of the FAO).
Some of us (police included) may think that police internal guidelines empower them to make a judgment call as to the degree of force used. Others may believe that police officers are only liable for criminal misconduct if they are not on duty. In both situations, they are thought to be somewhat “immune” to criminal liability. But both beliefs are quite mistaken.
Firstly, an internal guideline is, after all, a guideline. It does not override the law. Furthermore, no law in Hong Kong empowers a police officer to conduct punitive measures on any individual using force (even if he is a criminal suspect), which is apparently what the officer was trying to do in the video clip as he applied the pepper spray – to punish an individual rather than to prevent a crime. Any force used by a police officer with such aim would logically have to be deemed unnecessary and unlawful.